1. Field of the Invention
The present invention relates to an optical modulating device suitable for an active matrix type of display panel, and more particularly to an optical modulating device utilizable as an active matrix type of liquid crystal display panel provided with a matrix substrate which is incorporated with a driving semiconductor array.
2. Description of the Prior Art
In the fabrication of conventional display panels, there are difficulties in the registration of the substrate which supports row and column electrodes and semiconductor driving circuits in the proper position relative to the counter-electrode-supporting substrate. The quality of images formed on the resulting display panel is affected by the accuracy of the registration. In particular, when the counter-electrode-supporting substrate is provided with, for example, color filters, the superposition of the two substrates requires very precise registration in order that each color filter may exactly be registered in relation to the opposing dot electrode on the semiconductor driving circuit substrate. If the registration is not precise, color deviation will occur, leading to images of a poor quality.
Accordingly, in the conventional display panels, some marks are put on both substrates at the corresponding positions and the substrates are superposed based on the marks.
In such a conventional method of registration, however, a gap between the pair of marks causes difficulty in the exact registration of each color filter to the opposing dot electrode for the active matrix type of color display panel employing a semiconductor driving circuit substrate where high accuracy of registration is required. In display panels provided with segment electrodes, the registration tolerance can be enlarged by making the figure eight segment of one of the opposing segments larger in width that that of the other. However, in color display panels of the active matrix type, the tolerance of the registration of each color filter to the opposing dot electrode is extremely small, therefore requiring a higher accuracy of the registration between the substrates.